The Internet Protocol (“IP”) serves as the de-facto standard for forwarding data messages (“datagrams”) between network devices connected with the Internet. To that end, IP delivers datagrams across a series of Internet devices, such as routers and switches, in the form of one or more data packets. Each packet has two principal parts: (1) a payload with the information being conveyed (e.g., text, graphic, audio, or video data), and (2) a header, known as an “IP header,” having the address of the network device to receive the packet(s) (the “destination device”), the identity of the network device that sent the packet (the “originating device”), and other data for routing the packet.
Many people thus analogize packets to a traditional letter using first class mail, where the letter functions as the payload, and the envelope, with its return and mailing addresses, functions as the IP header.
Current Internet devices forward packets one-by-one based essentially on the address of the destination device in the packet header in accordance with an Internet routing protocol such as BGP, OSPFv2, IS-IS, etc. Among other benefits, this routing scheme enables network devices to forward different packets of a single datagram along different routes to reduce network congestion, or avoid malfunctioning network devices. Those skilled in the art thus refer to IP as a “stateless” protocol because, among other reasons, it does not save packet path data, and does not pre-arrange transmission of packets between end points.
Current Internet routing protocols generally cannot route packets from an element in one private network to an element in another private network because the IP address spaces used for elements in those private networks often overlap. These are often referred to as “unroutable” addresses, which are not useful on the public Internet.
Therefore, Network Address Translation (NAT) is often used to convert between local addresses used for routing within the private networks and public Internet addresses used for routing over the public Internet. The public Internet address is used to route packets between the private networks. Within each private network, other information in the packet is used to determine the local address used to route the packet to the destination entity within the destination private network.
Over the past decade, network challenges have evolved from bandwidth and broadband availability to security and mobility. Cloud has emerged as a primary service delivery architecture that achieves economies of scale unheard of in the past. Cloud embraces sharing of resources, including computing and storage. This has created a huge number of new requirements unmet by today's IP routing models, such as:                Private-network to private-networking models        Dynamically-arranged, service-specific Quality of Service        Unified IPv4 and IPv6 routing tables        Authenticated directional routing        On-the-fly encryption        Overlapping address support        Load balancing instead of equal-cost multipath (ECMP)        Integrated DPI and resulting flow analytics        
To meet these requirements, current architectures require middleboxes (e.g., firewalls, DPI devices, load balancers) mixed with overlay networking (e.g., VLANs, nested VLANs, VxLANs, MPLS, Cisco ACI, VMware NSX, Midonet) and orchestration (e.g., OpenStack, service function chaining).